In recent years, there has been a growing demand for formation of a fine pattern formation and ejection of a high-viscosity ink due to the progress of high-definition image quality by inkjet method and expansion in the scope of its application in the industrial field. If the conventional inkjet recording method is used to solve this problem, it is necessary to produce a very fine nozzle and to increase a pressure to eject high-viscosity ink. This requires higher drive voltage and increases cost of the head and the apparatus. Thus, no apparatus that can meet practical use had not been realized.
To meet the aforesaid demand, there is known a technology to eject high-viscosity as well as low-viscosity liquid droplets through a very fine nozzle, so-called electrostatic suction type liquid particle ejection technique wherein a liquid in the nozzle is electrostatically charged and is ejected by the electrostatic suction force received from the electric field formed between the nozzle and various types of substrates as objects for receiving the liquid droplets (Patent Document 1).
Also a development is being advanced to produce an liquid droplet ejection apparatus based on a so-called electric field assist method combining the aforementioned liquid particle ejection technique and the technology of ejecting liquid droplets by a pressure generating device through deformation of the piezoelectric element or generation of air bubbles inside the liquid (Patent Document 2 through 5). The electric field assist method is that, a liquid meniscus is risen on the ejection hole of the nozzle using a meniscus forming device which is a pressure generation device such as a piezoelectric element and the electrostatic suction force thus an electrostatic suction force with respect to the meniscus is increased, and the meniscus is formed into a liquid droplet while overcoming a liquid surface tension, with the result that the liquid droplet is ejected.
[Patent Document 1] International Publication No. 03/070381 (Booklet)
[Patent Document 2] Unexamined Japanese Patent Application Publication No. H5-104725
[Patent Document 3] Unexamined Japanese Patent Application Publication No. H5-278212
[Patent Document 4] Unexamined Japanese Patent Application Publication No. H6-134992
[Patent Document 5] Unexamined Japanese Patent Application Publication No. 2003-53977